This paper describes the steps involved in a clinical plan for developing MDMA-assisted therapy as a clinical treatment for posttraumatic stress disorder, preceded by a rationale for the selection of the particular substance and condition to be treated. While the author acknowledges that the physiological safety profile of MDMA is less strong than other psychedelics (LSD, psilocybin), and may pose risks of neurotoxicity in some doses or settings, the author argues that MDMA has a stronger psychological safety profile. It is noted that MDMA is also short-acting when compared with classical psychedelics, and subjective effects are more readily recalled and integrated when not in the substance-induced state. Because they both are associated with anxiety and psychological distress, both terminal illness and PTSD are suggested as ideal targets for MDMA-assisted therapy. In particular, the potential for MDMA-assisted therapy to allow people to approach upsetting thoughts, feelings or memories may prove beneficial to people with PTSD. Because people with PTSD are more likely to be in better health than people with terminal illnesses, and people with PTSD will be taking little or no other necessary medication that might interact with MDMA, the author proposes that PTSD presents a better target for MDMA-assisted therapy than does terminal illness. Methodological issues encountered in study design (such as the need for a between-subjects design and the merits of placebo versus active placebo) are addressed, as are issues of sample size and the treatment duration needed to demonstrate efficacy. The paper then describes a sequence of steps for developing MDMA-assisted therapy as a treatment for PTSD, following FDA guidelines. The clinical plan, and some of the discussion of study design has been described previously in the unpublished doctoral dissertation by the same author (Doblin 2001) available online at http://www.maps.org/dissertation/)